1. Field of the Invention
The invention relates to apparatus for conducting a process of reforming gasolines, under low pressure, in the presence of at least one catalyst, in which process the heat required for the reaction is brought by a smoke-based heat-carrying fluid coming, for example, from the combustion of air with a hydrocarbon mixture, for example natural gas or refinery gas.
2. Description of the Prior Art
It is known to improve the quality of gasolines, and particularly their octane number, by reforming at about 500.degree. C., in the presence of hydrogen, in several solid catalytic beds comprising precious metals activated by different additives, such as rhenium and iridium for example (patents U.S. Pat. No. 4,588,495, FR-B-2,593,324, FR-B-2,597,496, FR-B-2,600,668).
The reforming of gasolines results from a combination of reactions whose balance is overall endothermic and a drop of the reaction pressure usually occurs as the transformations progress.
The traditional method of reforming gasolines comprises three, and generally four, adiabatic reactors, disposed in series and connected together by two, and generally three, heating ovens, whose role is to heat the reagents and to bring and maintain their temperature thus in the desired reaction temperature range.
The application of anti-pollution standards leads to a reduction of the lead concentration in gasolines and will in the long run result in suppressing organo-plumbic additives in motor car fuels for controlled ignition engines. Such regulations impose on refiners an increase in the severity of the operating conditions of the reforming units so as to satisfy the criteria of quality required for satisfactory operation of the motor vehicle engines: thus, refiners are led to reduce more and more the operating pressure of these reforming units. In fact, if the severity of the operating conditions is increased, in particular the octane number of the reformed products, the yield drops and the only means of compensating for such a drop of yield is to operate at a lower pressure.
But such low pressure operation is expensive and R. G. McClung et al. have recently shown (Hydrocarbon Processing, September 1983, pages 80-84) that such a system cannot actually go down below the limit of 1 MPa without serious drawbacks.
The major obstacle is due in particular to the pressure drop (for example 0.4-0.5 MPa) of the unit constructed from such a reaction system.